Expertise

Practices

Location

Kent, Washington

After Hurricane Katrina, the Federal Emergency Management Agency (FEMA) and the US Army Corps of Engineers enacted a series of policy changes that have affected communities across the nation. In addition to new design and construction guidelines for levees and new processes for determining flood insurance rate maps, the Corps placed the responsibility for levee certification on the local communities that levees protect. The City of Kent, with the Green River flowing through it, proactively realized the implications of these policy changes on their community and contacted GeoEngineers as a trusted advisor to guide them through the new and unfamiliar process.

Completing detailed stability, seepage, piping and settlement analyses to US Army Corps of Engineers guidelines

Completing seismic characterization of site and liquefaction analyses

Developing an operations and maintenance manual

Providing consultation during the peer-review and levee-certification process

Providing consultation during design and development of plans and specifications

Approach

When the Corps’ levee certifications expired, so did their granted variances to the City of Kent for plants and trees along the levees. GeoEngineers worked with the city to develop levee vegetation management plans and operations and maintenance manuals, which were critical to maintaining both required safety standards and riparian vegetation, plants that help with soil conservation and habitat biodiversity. The vegetation maintenance approach that GeoEngineers developed for the Horseshoe Bend Levee, the first third-party certification of a Corps’ levee in Region X, became the standard for all levee vegetation maintenance manuals along the Green River in Kent.

Results

Our levee work for the City of Kent has helped maintain low flood insurance rates for hundreds of local residents and businesses. The Horseshoe Bend and Foster Park levees are under construction and have received FEMA certification. The submittals for the Hawley Road, Briscoe and Desimone levees have received no further technical comments and are awaiting final approval.

Innovation

When the federal government revised seismic standards two years after GeoEngineers completed seismic analysis on two important levees protecting the Kent Valley, we used innovative numerical modeling techniques that gave the City of Kent and the design team confidence that the old levees met the new standards.